Thomas de Groot wrote:


> I think now that an easier workflow would be to slice a pie section from a 
> featureless shaft, exactly covering one flute width and twice the half rib 
> widths; to craft the flute and finally to apply a rotational sweep to 
> restore the complete shaft.
>

Thanks for that.  Probably how I will proceed.



> 
>>>If you want to follow the classical rules, number and form of the flutes 
>>>are fixed, but that is another discussion entirely.
>>
>>I would be intereseted if you have any references.  Right now I am using 
>>18 flutes, so a 20 degree rotation.
> 
> 24 seems to have been the general use in antiquity, at least in the 
> classical period. However, older columns could have up to 48 flutes. Ribs 
> were sharp during the Doric Order period, but flat (with deeper flutes) 
> later.
> 
>>

Interesting.  I have been making counts of visible flutes on coluns here 
and there, (including the new MMA classical wing,) then doubling the 
number, but it never seems quite that many.  I will have to pay closer 
attention.

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46c5dabe$1@news.povray.org...
> Shay wrote:
>
>
>
> I am not really sure there is support for an interpolated or function 
> driven reduction of the radius in the sphere_sweep syntax but I have only 
> ever looked at it briefly. In any case I still would not be able to 
> compose such a function.
>
Does that  fit your needs?

#declare P1=.7;
#declare P2=.9;
#declare P3=1.1;
#declare P4=1.15;


#declare Shaft=
sphere_sweep {

  cubic_spline

  5,
  <0, 7.5, 0>, P1
  <0, 5.5, 0>, P2
  <0, 0, 0>,P3
  <0, -5.5, 0>,P4
  <0, -7.5, 0>, P4
  pigment {color rgb 1 }
}

 #declare Flute =
  sphere_sweep {
  cubic_spline
  5,
  <P1, 7.5, 0>, 0.1
  <P2, 5, 0>, .1
  <P3, 0, 0>, .1
  <P4, -5, 0>,.1
  <P4, -7.5, 0>, .1
pigment {color rgb 1  }
}

#declare Flutes= union{
#declare C_Flute =0;

#while (C_Flute<20)
object{Flute rotate y*18*C_Flute}
   #declare C_Flute =C_Flute+1;
#end
}
difference{
object{Shaft}
object{Flutes}
}

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M_a_r_c wrote:

Thanks, yes, the constant radius on your flutes are one of the problems 
I wanted to overcome, but obviously, tha can be adjusted by eyeball or a 
static calulation beforehand, and I now see the possibilities.  Also it 
renders much faster than my spline solution.

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46c615ec$1@news.povray.org...
> M_a_r_c wrote:
>
> Thanks, yes, the constant radius on your flutes are one of the problems I 
> wanted to overcome, but obviously, tha can be adjusted by eyeball or a 
> static calulation beforehand, and I now see the possibilities.  Also it 
> renders much faster than my spline solution.

I didn't study the greek architecture, it's a fast try at a sphere_sweep 
solution as Shay suggested :-)
I wondered wether the flute radius had to be constant or not but I see no 
problem at making it vary as a fraction of the shaft radius.
That's better I think.


#declare P1=.7;
#declare P2=.9;
#declare P3=1.6;  // Obelix nudged my elbow here ;-) just to show as flute 
radius follows shaft radius... better with 1.1
#declare P4=1.15;


#declare Shaft=
sphere_sweep {

  cubic_spline

  5,
  <0, 12.5, 0>, P1
  <0, 10.0, 0>, P2
  <0, 5, 0>,P3
  <0, 0.0, 0>,P4
  <0, -2.5, 0>, P4

}

#local N_flutes=20; //Number of flutes
#local Flute_Ratio=.95; //flute radial coverage
#local F_fctr=pi*Flute_Ratio/N_flutes;

 #declare Flute =
  sphere_sweep {
  cubic_spline
  5,
  <P1,  12.5,  0>, F_fctr*P1
  <P2,   10,   0>, F_fctr*P2
  <P3,   5,   0>, F_fctr*P3
  <P4,  0,   0>, F_fctr*P4
  <P4,  -2.5, 0>, F_fctr*P4
}

#declare Flutes= union{
#declare C_Flute =0;

#while (C_Flute<20)
object{Flute rotate y*C_Flute*360/N_flutes}
   #declare C_Flute =C_Flute+1;
#end
}
difference{
object{Shaft}
object{Flutes}
 pigment {color rgb 1 }
}

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46c6b8cb$1@news.povray.org...
Last one, I think, now radius and y coordinate declared in the same 2d 
vector
// radius and y coordinate declared in same 2d vector

#declare P1=<.7,12.5>;
#declare P2=<.9,10>;
#declare P3=<1.1,5>;
#declare P4=<1.15,0>;
#declare P5=<1.1,-2.5>;



#declare Shaft=
sphere_sweep {

  cubic_spline

  5,
  <0, P1.y, 0>, P1.x
  <0, P2.y, 0>, P2.x
  <0, P3.y, 0>, P3.x
  <0, P4.y, 0>, P4.x
  <0, P5.y, 0>, P5.x

}

#local N_flutes=25; //Number of flutes
#local Flute_Ratio=.9; //flute radial coverage
#local F_fctr=pi*Flute_Ratio/N_flutes;

 #declare Flute =
  sphere_sweep {
  cubic_spline
  5,
  <P1.x, P1.y, 0>, F_fctr*P1.x
  <P2.x, P2.y, 0>, F_fctr*P2.x
  <P3.x, P3.y, 0>, F_fctr*P3.x
  <P4.x, P4.y, 0>, F_fctr*P4.x
  <P5.x, P5.y, 0>, F_fctr*P4.x
}

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46c6c1cf$1@news.povray.org...
Ooops

 #declare Flute =
  sphere_sweep {
  cubic_spline
  5,
  <P1.x, P1.y, 0>, F_fctr*P1.x
  <P2.x, P2.y, 0>, F_fctr*P2.x
  <P3.x, P3.y, 0>, F_fctr*P3.x
  <P4.x, P4.y, 0>, F_fctr*P4.x
  <P5.x, P5.y, 0>, F_fctr*P5.x  // not F_fctr*P4.x as in previous post
 }


Marc

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M_a_r_c wrote:

> 46c6c1cf$1@news.povray.org...
> Ooops
> 
>  #declare Flute =
>   sphere_sweep {
>   cubic_spline
>   5,
>   <P1.x, P1.y, 0>, F_fctr*P1.x
>   <P2.x, P2.y, 0>, F_fctr*P2.x
>   <P3.x, P3.y, 0>, F_fctr*P3.x
>   <P4.x, P4.y, 0>, F_fctr*P4.x
>   <P5.x, P5.y, 0>, F_fctr*P5.x  // not F_fctr*P4.x as in previous post
>  }
> 
> 
> Marc 
> 
> 
Poifect!  Thanks, I am immediately switching to this method.

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